1. Field of the Invention
This invention relates in general to micro mixers, and more specifically to micro mixers utilizing time-varying force fields to induce bulk fluid and/or sample component motion leading to homogenization of sample components.
2. Description of Related Art
Nano/Micro (“micro”) devices have generally been developed to improve the speed, accuracy and cost efficiency of analytical methods for chemical, biological, engineering or medical applications. However, scaling down analytical systems results in changes to the relative magnitudes of various forces involved in the analytical system. Therefore, an improved efficiency in one task of a microdevice could be replaced by a loss of efficiency in another task in the microdevice.
Most analytical microdevices require the mixing of multiple fluids, the mixing of components embedded in a fluidic medium, or the homogenization of components distributed in a chamber. In micro scale devices, viscous effects greatly diminish fast mixing. Micro scale flows are characterized by low Reynolds numbers. Hence, instabilities cannot develop, and the effective mixing mechanisms which occur in turbulent flows (high Reynolds number) do not occur. Existing micro mixing methods rely on molecular diffusion to homogenize sample and/or reaction components. However, this mechanism results in a large time cost due to the slow rate at which diffusion naturally occurs. Thus, decreasing channel size leads to a shorter diffusion time, as diffusion varies with the second power of the characteristic dimension of the channel.
However, other methods may be employed to speed mixing of samples in a microdevice. For example, a first sample can be forced through a 2-D nozzle array into a second sample, so that the mixing interface is increased, and thereby the diffusion time required for mixing the two samples is reduced. Another technique for mixing samples in a microdevice is to use at least one mechanical pump to control the filling and/or removal of the sample components into and out of a closed cavity, producing fluid motions. However, these micro mixing methods require a high energy input, and additional mechanical components which increase the size and complexity, and therefore decrease the efficiency, of the microdevice. Therefore, there is a need for a micro mixer to facilitate the efficient homogenization of sample components in microdevices.